Dependences of Specific Loss Power on Magnetic Field and Frequency in Elongated Platelet $\gamma$ -Fe $_{2}$ <

Elongated platelet γ-Fe₂O₃ particles with particle sizes of about 30 to 100 nm were prepared for magnetic thermoablation using hysteresis-loss heating of the ferromagnetic particles. The coercive force was based on the shape anisotropy of the elongated shape. The dependences of specific loss power (SLP) on the magnetic field strength and frequency were examined for particles in the range of 133 to 640 Oe and 117 to 429 kHz, respectively. The dependence of SLP on the magnetic field was similar to that of areas in minor hysteresis loops and showed that the heat generation in the particles was almost entirely based on hysteresis loss. To realize effective hysteresis-loss heating a magnetic field about four times stronger than the coercive force of particles was necessary. The SLP increased linearly with increasing frequency. Particles with a coercive force of 153 Oe showed an SLP of 1670 W/g under a magnetic field of 500 Oe and at a frequency of 429 kHz.